/*!
* \brief Do fast non-dominated sort and evaluate Pareto fronts of data up to given size.
* \param outParetoFronts Pareto fronts from the fast ND sort.
* \param inSortStop Number of individuals on the Pareto fronts needed to stop the sort.
* \param inIndividualPool Pool of individuals to get next Pareto front of.
* \param ioContext Evolutionary context.
*/
void EMO::NSGA2Op::sortFastND(NSGA2Op::Fronts& outParetoFronts,
unsigned int inSortStop,
const Individual::Bag& inIndividualPool,
Context& ioContext) const
{
Beagle_StackTraceBeginM();
outParetoFronts.clear();
if(inSortStop == 0) return;
outParetoFronts.resize(1);
unsigned int lParetoSorted = 0;
// N: Number of dominating individuals
std::vector<unsigned int> lN(inIndividualPool.size(), 0);
// S: Set of dominated individuals
Fronts lS(inIndividualPool.size());
// First pass to get first Pareto front and domination sets
for(unsigned int i=0; i<inIndividualPool.size(); ++i) {
Fitness::Handle lFitI = inIndividualPool[i]->getFitness();
for(unsigned int j=(i+1); j<inIndividualPool.size(); ++j) {
Fitness::Handle lFitJ = inIndividualPool[j]->getFitness();
if(lFitJ->isDominated(*lFitI)) {
lS[i].push_back(j); // Add index j to dominated set of i
++lN[j]; // Increment domination counter of j
} else if(lFitI->isDominated(*lFitJ)) {
lS[j].push_back(i); // Add index i to dominated set of j
++lN[i]; // Increment domination counter of i
}
}
if(lN[i] == 0) { // If i is non-dominated
outParetoFronts.back().push_back(i);
++lParetoSorted;
}
}
Beagle_LogVerboseM(
ioContext.getSystem().getLogger(),
uint2ordinal(1)+std::string(" Pareto front consists of ")+
uint2str(outParetoFronts.back().size())+" individuals"
);
// Continue ranking until individual pool is empty or stop criterion reach
while((lParetoSorted < inIndividualPool.size()) && (lParetoSorted < inSortStop)) {
unsigned int lIndexLastFront = outParetoFronts.size() - 1;
outParetoFronts.resize(outParetoFronts.size() + 1);
for(unsigned int k=0; k<outParetoFronts[lIndexLastFront].size(); ++k) {
unsigned int lIndexPk = outParetoFronts[lIndexLastFront][k];
for(unsigned int l=0; l<lS[lIndexPk].size(); ++l) {
unsigned int lIndexSl = lS[lIndexPk][l];
if(--lN[lIndexSl] == 0) {
outParetoFronts.back().push_back(lIndexSl);
++lParetoSorted;
}
}
}
Beagle_LogVerboseM(
ioContext.getSystem().getLogger(),
uint2ordinal(outParetoFronts.size())+std::string(" Pareto front consists of ")+
uint2str(outParetoFronts.back().size())+" individuals"
);
}
Beagle_StackTraceEndM();
}
/*!
* \brief Apply NPGA2 multiobjective selection operator.
* \param ioDeme Deme on which selection operator is applied.
* \param ioContext Evolutionary context.
*/
void NPGA2Op::operate(Deme& ioDeme, Context& ioContext)
{
Beagle_StackTraceBeginM();
if(ioDeme.size() == 0) return;
Beagle_LogTraceM(
ioContext.getSystem().getLogger(),
std::string("Applying NPGA2 multiobjective selection on the ")+
uint2ordinal(ioContext.getDemeIndex()+1)+" deme"
);
std::vector<bool> lAlreadySelectedIndiv(ioDeme.size(), false);
Individual::Bag lSelectedIndividual;
const Factory& lFactory = ioContext.getSystem().getFactory();
// Generate new generation by selection
for(unsigned int i=0; i<ioDeme.size(); ++i) {
// First participant
unsigned int lFirstParticipant =
ioContext.getSystem().getRandomizer().rollInteger(0, ioDeme.size()-1);
std::vector<unsigned int> lNDParticipants(1, lFirstParticipant);
// Following participants to tournament
for(unsigned int j=1; j<mNumberParticipants->getWrappedValue(); ++j) {
unsigned int lParticipant =
ioContext.getSystem().getRandomizer().rollInteger(0, ioDeme.size()-1);
// Test if participant is dominated or dominate other participants
bool lIsDominated = false;
Fitness::Handle lPartFitness = ioDeme[lParticipant]->getFitness();
for(unsigned int k=0; k<lNDParticipants.size(); ++k) {
Fitness::Handle lFitnessNDk = ioDeme[lNDParticipants[k]]->getFitness();
if(lPartFitness->isDominated(*lFitnessNDk)) {
lIsDominated = true;
} else if(lFitnessNDk->isDominated(*lPartFitness)) {
lNDParticipants.erase(lNDParticipants.begin()+k);
}
}
if(lIsDominated==false) lNDParticipants.push_back(lParticipant);
}
// Test if there is a tie. If so evaluate niche count.
Beagle_AssertM(lNDParticipants.size() != 0);
unsigned int lWinner = lNDParticipants[0];
if(lNDParticipants.size() > 1) {
float lLowestNicheCount = evalNicheCount(*ioDeme[lNDParticipants[0]], lSelectedIndividual);
for(unsigned int j=1; j<lNDParticipants.size(); ++j) {
float lNicheCount = evalNicheCount(*ioDeme[lNDParticipants[j]], lSelectedIndividual);
if(lNicheCount < lLowestNicheCount) {
lLowestNicheCount = lNicheCount;
lWinner = lNDParticipants[j];
}
}
}
// Put winner in selected individual bag
if(lAlreadySelectedIndiv[lWinner]) {
std::string lIndividualType = ioDeme[lWinner]->getType();
Individual::Alloc::Handle lIndividualAlloc =
castHandleT<Individual::Alloc>(lFactory.getAllocator(lIndividualType));
Individual::Handle lIndividual = castHandleT<Individual>(lIndividualAlloc->allocate());
lIndividual->copy(*ioDeme[lWinner], ioContext.getSystem());
lSelectedIndividual.push_back(lIndividual);
Beagle_LogVerboseM(
ioContext.getSystem().getLogger(),
uint2ordinal(lWinner+1)+" individual selected again in NPGA2 selection process"
);
} else {
lSelectedIndividual.push_back(ioDeme[lWinner]);
lAlreadySelectedIndiv[lWinner] = true;
Beagle_LogVerboseM(
ioContext.getSystem().getLogger(),
uint2ordinal(lWinner+1)+" individual selected in NPGA2 selection process"
);
}
}
// Copy selected individuals into deme
for(unsigned int j=0; j<ioDeme.size(); ++j) ioDeme[j] = lSelectedIndividual[j];
Beagle_StackTraceEndM();
}
